Module Name: src Committed By: riastradh Date: Thu Mar 10 00:14:34 UTC 2022
Modified Files: src/sys/dev/pci: gffb.c Log Message: gffb(4): Nix membar_sync and explain what's going on here. To generate a diff of this commit: cvs rdiff -u -r1.18 -r1.19 src/sys/dev/pci/gffb.c Please note that diffs are not public domain; they are subject to the copyright notices on the relevant files.
Modified files: Index: src/sys/dev/pci/gffb.c diff -u src/sys/dev/pci/gffb.c:1.18 src/sys/dev/pci/gffb.c:1.19 --- src/sys/dev/pci/gffb.c:1.18 Thu Mar 10 00:14:25 2022 +++ src/sys/dev/pci/gffb.c Thu Mar 10 00:14:33 2022 @@ -1,4 +1,4 @@ -/* $NetBSD: gffb.c,v 1.18 2022/03/10 00:14:25 riastradh Exp $ */ +/* $NetBSD: gffb.c,v 1.19 2022/03/10 00:14:33 riastradh Exp $ */ /* * Copyright (c) 2013 Michael Lorenz @@ -35,7 +35,7 @@ */ #include <sys/cdefs.h> -__KERNEL_RCSID(0, "$NetBSD: gffb.c,v 1.18 2022/03/10 00:14:25 riastradh Exp $"); +__KERNEL_RCSID(0, "$NetBSD: gffb.c,v 1.19 2022/03/10 00:14:33 riastradh Exp $"); #include <sys/param.h> #include <sys/systm.h> @@ -1133,12 +1133,23 @@ gffb_putchar(void *cookie, int row, int if (rv == GC_OK) return; + /* + * Use gffb_sync to wait for the engine to become idle before + * we start scribbling into VRAM -- we woudn't want to stomp on + * a scroll in progress or a prior glyphcache_add that hasn't + * completed yet on the GPU. + */ mutex_enter(&sc->sc_lock); gffb_sync(sc); sc->sc_putchar(cookie, row, col, c, attr); - membar_sync(); mutex_exit(&sc->sc_lock); + /* + * If glyphcache_try asked us to, cache the newly written + * character. This will issue a gffb_bitblt which will wait + * for our CPU writes to the framebuffer in VRAM to complete + * before triggering GPU reads from the framebuffer in VRAM. + */ if (rv == GC_ADD) { glyphcache_add(&sc->sc_gc, c, x, y); }